JP3101956B2 - Netting support members for paper machines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a member for abutting and supporting a net in a paper machine.

[0002]

2. Description of the Related Art As shown in FIG. 3, a structure of a paper machine conventionally used is a papermaking net 2 rotated by a roll 3 in the direction of an arrow, and a supporting member 1 disposed below the papermaking net 2. A slurry 5 made of a pulp material is supplied from the head box 4 to the upper part of the netting 2, and the netting 2 is supported by the support member 1 and the slurry 5 is dewatered.

Further, as a material of the support member 1, a plastic material such as ultra-high molecular weight polyethylene is inexpensive, so that it was widely used before. However, because of the presence of clay and talc in the pulp raw material and abrasion in a short time due to the contact sliding with the papermaking net 2, the support member 1 is removed from the paper machine and the surface is polished or replaced. Maintenance such as work had to be performed frequently.

Therefore, in recent years, ceramics containing alumina, zirconia, silicon nitride or the like as a main component have been widely used as a material of the support member 1 (for example, Japanese Patent Application Laid-Open No. 55-80).
591 and JP-A-58-208485). The support member 1 made of these ceramics has been widely used because of its high abrasion resistance and long service life.

On the other hand, such a support member 1 is usually fixed to a support base (box) 6 made of stainless steel or the like with bolts, or is fixed by inserting it into a fitting portion provided on the support base 6. Methods have been adopted. In addition, the ceramic supporting member 1 allows the meshing net 2 to be abutted and supported to run smoothly without being damaged, and to appropriately perform a dehydration (scraping of water) action from the meshing net 2. The design has been made with attention to the cross-sectional shape and the outer peripheral shape so that the edge portion of the member 1 does not crack or chip. In particular, the tip of the support member 1 to which the papermaking net 2 first comes into contact and contributes to the dewatering action is
It is formed at an acute angle and its surface is carefully finished.

[0006]

However, in recent paper machines, the speed of the net making machine 2 is greatly increased in terms of improvement in productivity, and the wear resistance of the support member 1 is further required. ing. On the other hand, the conventional support member 1 made of ceramics such as alumina, zirconia, and silicon nitride could not sufficiently satisfy this requirement.

In the case of alumina and silicon nitride, the leading edge of the support member 1 is liable to be chipped, and the chipping or the like shortens the life of the screen-making net 2 or reduces the life of the sheet-making net 2. There has been a problem that the dewatering action is reduced, and uniform quality of the paper cannot be maintained, leading to deterioration of the paper quality.

In view of the above, an object of the present invention is to provide a net-making support member having characteristics of high wear resistance based on high hardness and low occurrence of chipping due to high toughness.

[0009]

SUMMARY OF THE INVENTION In view of the above, the gist of the present invention is based on the use of ceramics containing silicon carbide as a main component. Among them, as a result of earnest research by the inventor,
It has been found that a material obtained by adding a metal oxide as a sintering aid and performing liquid phase sintering is the most suitable as a net forming support member.

That is, such a silicon carbide ceramic has a Vickers hardness of 1500 to 2500 kg / mm ^2.
In addition to having high wear resistance and high abrasion resistance, and having excellent slidability, abrasion on a paper net can be reduced. In addition, by adding metal oxides and performing liquid phase sintering,
The fracture toughness value (K _1c ) can be increased to 4 to 6 MPa√m, and when the angle of the leading edge of the support member is 75 °, the number of chips of 0.2 mm or less generated per 100 mm is reduced to 4 or less. And the occurrence of chipping can be reduced. Therefore, the amount of wear on the papermaking net due to these chippings can be reduced. Further, since the silicon carbide ceramics of the present invention has a high thermal conductivity of 60 W / m · K or more, the frictional heat generated by sliding with the net is radiated to the entire block body. Therefore, the net can be protected and the life of the net can be prolonged.

In the present invention, the metal oxide to be added as a sintering aid to the silicon carbide ceramics includes:
Al ₂ O ₃ may be added in an amount of 1 to 7%, and an oxide of a Group 3a element such as Y ₂ O ₃ or CeO ₂ may be added in an amount of 0.1 to 5%. These metal oxides, as sintering aids, enhance the sintering properties of silicon carbide ceramics and form a grain boundary phase between silicon carbide crystal grains in the sintered body to prevent cracks from developing. Has the effect of increasing the toughness. However, if the addition amount is too large, the hardness and strength will be low,
Those in the above range are preferred.

In the silicon carbide-based ceramic of the present invention, the average crystal grain size is preferably 10 μm or less, and more preferably 0.5 to 6 μm. This is because, when the average crystal particle diameter exceeds 10 μm, the strength is deteriorated, and a sharp edge at the tip cannot be formed when used as a support member, so that the dewatering action deteriorates.

Further, the silicon carbide ceramic of the present invention has an open porosity of 1% or less, preferably 0.3% or less. This is because if the open porosity is larger than 1%, the strength is reduced and sharp edges are hardly produced.

[0014]

Embodiments of the present invention will be described below.

FIG. 1 shows a net supporting member 1 for a paper machine according to the present invention.
Is shown. The support member 1 includes a base 11 and a tip member 12 fixed thereto, and a tip edge portion 13 of the tip member 12 is formed at an acute angle and has a sharp edge. The tip member 12 is made of a silicon carbide ceramic having a fracture toughness value (K _1C ) of 4 MPa√m or more, which is mainly composed of silicon carbide, is added with a metal oxide, and is subjected to liquid phase sintering. The base 11 is made of alumina ceramics.

Then, the support member 1 is fixed to a support base 6 as shown in FIG.
The dewatering action can be performed by sliding the papermaking net 2 to which the slurry 5 composed of the pulp raw material is supplied.

At this time, the supporting member 1 of the present invention has excellent wear resistance, slidability, and chipping resistance because the tip edge portion 13 is made of high-toughness silicon carbide ceramics. 2 can be extended.

In the embodiment shown in FIG. 1, only the tip member 12 is formed of silicon carbide ceramic in order to reduce the cost. However, as another embodiment, the entire support member 1 is integrally formed of silicon carbide ceramic. It can also be formed as desired.

EXPERIMENTAL EXAMPLE 1 First, an experiment was conducted to examine the slidability between various ceramics and the net 2.

As shown in FIG. 4, a plastic wire 22 is wound on the rotating ceramic roll 21 as the net 2 and a load is applied to the wire 22 with a weight 23. A slurry 24 composed of an aqueous solution of talc is dropped by a predetermined amount on a sliding portion between the ceramic roll 21 and the wire 22. In this state, the ceramic roll 21 was rotated, the weight loss of the plastic wire 22 was measured, and the wear amount was evaluated. The surface roughness of the sliding surface of the ceramic roll 21 was also measured. The test conditions were as follows: (a) Slurry: 2% aqueous solution of talc, 0.7 to
0.75 liter / minute (b) Wire: plastic (c) Weight Copper: 850 g (d) Roll size: φ60 mm (e) Roll rotation speed: 1500 rpm As the material of the ceramic roll 21, silicon carbide ceramics containing Al ₂ O ₃ and Y ₂ O ₃ were prepared as examples of the present invention, and alumina ceramics, zirconia ceramics, and silicon nitride ceramics were prepared as comparative examples.

As a result, the weight loss of the wire 22 is shown in FIG.
As shown in (A), the silicon carbide ceramics of the present invention has a smaller weight loss of the wire 22 and a smaller effect on the wire 22 than alumina and zirconia. Further, as shown in FIG. 5B, the surface roughness of the ceramic roll 21 is changed, and the silicon carbide-based ceramic of the present invention has a small surface roughness and a small and stable fluctuation as compared with other materials. . Therefore, the silicon carbide ceramics of the present invention has a low sliding resistance with the wire 22 and the wire 2
It turns out that the familiarity with 2 is good.

EXPERIMENTAL EXAMPLE 2 Next, in the same manner as described above, an experiment was conducted to examine the amount of wear on the ceramic side.

As shown in FIG. 6, four ceramic blocks 26 are fixed to the outer periphery of the roll 25 at equal intervals, and
And a load is applied to the wire 22 with a weight 23. In this state, continuous rotation was performed while a slurry 24 composed of an aqueous solution of talc was dropped on the sliding portion between the roll 25 and the wire 22, and the weight loss of the ceramic block 26 was measured to evaluate the wear amount. The test conditions were as follows: (a) Slurry: 2% aqueous solution of talc, 0.7 to
0.75 liter / min (b) Wire: metal (bronze) (c) Weight copper: 120 g (d) Roll size: φ60 mm (e) Roll rotation speed: 1500 rpm (f) Ceramic shape: 5 × 10 × 40 mm . The material of the ceramic block 26 was the same as that of the above-described experimental example 1.

As shown in FIG. 7, the wear amount of the silicon carbide ceramic of the present invention is much smaller than that of other materials, and the wear resistance against wire sliding is extremely high. The reason for this is not only that the hardness of the silicon carbide ceramics is high, but also that the wire 22
This is because they have excellent slidability and heat dissipation.

EXPERIMENTAL EXAMPLE 3 Next, as shown in FIG. 1, various ceramic materials were stuck as the tip member 12 of the support member 1, and an operation was carried out by incorporating the ceramic material into an actual paper machine to check the wear amount of the ceramics. Was done. The conditions of use of this paper machine were as follows: (a) Paper speed: 650 m / min (b) Paper: high quality paper (c) Paper net: Plastic (d) Experimental period: 6 months

Table 1 shows the ceramic materials used in this test and their characteristics. Further, for each material, as shown in FIG. 2, the wire contact width h, the wear height t, and the center line average roughness of this part after the test were measured. Table 2 shows the results.

[0027]

[Table 1]

[0028]

[Table 2]

In Table 1, SiC-A to D are silicon carbide ceramics of the present invention to which a metal oxide has been added, and have high fracture toughness (K _1C ) of 4 MPaＭＰm or more. SiC-E is a comparative example obtained by solid-phase sintering using the same silicon carbide ceramic but using boron (B) and carbon (C) instead of a metal oxide as an additive. The toughness value (K _1C ) is as low as 3.4 MPa√m.

In Table 2, the wear amount can be evaluated by the product of the wire-contact width a and the wear height h.
It is apparent from Table 2 that alumina, zirconia, and silicon nitride as comparative examples have a large amount of wear. This is because these ceramics have a somewhat low hardness and poor slidability with wires. In addition, S which is a comparative example
Although iC-E was excellent in hardness and slidability, chipping was likely to occur due to low toughness, and as a result, the amount of wear was large.

On the other hand, the silicon carbide (SiC) of the present invention
-A to D) show that the amount of wear is extremely small. Further, it can be seen that the surface roughness of the contact surface with the wire is small, and the sliding friction with the wire and damage to the wire are reduced. This is because the silicon carbide of the present invention is excellent in hardness and slidability and has high toughness, so that chipping hardly occurs.

Experimental Example 4 Further, each of the ceramic materials shown in Table 1 was machined with a diamond grindstone under the same conditions, and the leading edge 13 was finished at an angle of 75 °. At this time, the number of chips generated per 100 mm of the length of each ceramic material was measured.

[0033]

[Table 3]

From these results, it can be seen that the silicon carbide (SiC) of the present invention
-A to D) are slightly inferior to zirconia in chipping resistance, but are far superior to other materials. In addition, low toughness silicon carbide (SiC-
E) has a considerably higher number of times of chipping than the silicon carbide of the present invention.
It can be seen that a large difference occurs in the chipping resistance.

[0035]

As described above, according to the present invention, at least the leading edge portion of the member abutting and supporting the net making in the paper machine is required to have a fracture toughness value (K _1c ) of 4 MPa√m or more and the leading edge portion. When the angle is set to 75 °, the chipping of 0.2 mm or less per 100 mm is made of four or less silicon carbide ceramics, so that the wear resistance and chipping resistance of the support member itself are high. In addition, since the slidability with the net is good, the net can be hardly worn. Therefore, it is possible to use the supporting member and the net making machine well over a long period of time, and it is possible to provide a netting supporting member for a paper machine having excellent effects such as being able to be suitably used for a recent high-speed paper machine. .

[Brief description of the drawings]

FIG. 1 is a perspective view showing a net making support member for a paper machine of the present invention.

FIG. 2 is an enlarged side view of a portion A in FIG.

FIG. 3 is a schematic view showing the structure of a paper machine.

FIG. 4 is a schematic diagram showing a sliding test device for various ceramic materials and wires.

FIG. 5 (A) is a graph showing weight loss of a wire;
(B) is a graph showing the surface roughness of the ceramic roll.

FIG. 6 is a schematic diagram showing a sliding test apparatus for various ceramic materials and wires.

FIG. 7 is a graph showing weight loss of a ceramic block.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Support member 11 ... Base 12 ... Tip member 13 ... Tip edge part 2 ... Netting 3 ... Roll 4 ... Head box 5 ... Slurry 6 ... Support base

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) D21F 1/52

Claims (1)

(57) [Claims] A member having a fracture toughness value (K _1c ) of at least 4 at the leading edge of a member that abuts and supports a papermaking net in a paper machine.
MPa√m or more and the angle of the leading edge is 75 °
Wherein a notch of 0.2 mm or less per 100 mm is formed of four or less silicon carbide-based ceramics.